Production of sensitive gas sensors using CuO/SnO2 nanoparticles

Metal oxide nanoparticles, such as CuO and SnO2, are outstanding systems for H2S gas sensing in air. In this work, those nanoparticles were deposited with different mixing percentages on substrates to form percolating networks of nanoparticles. Electrical electrodes were deposited on the nanoparticles’ films to investigate their gas sensing response against H2 and H2S, and their electrical characteristics. The sensor devices based on CuO–SnO2 nanoparticles revealed enhanced sensing characteristics against H2S with a sensitivity of 10 ppm. The enhanced sensing characteristics could be attributed to the formation of PN-junctions among CuO and SnO2 nanoparticles. The reasonable production cost (due to simple structure and cheap used materials), low power consumption ( ~ 1 µW for H2S at room temperature), high sensitivity, high response, and reasonable response time of the present sensors qualify them for practical implementation in portable gas sensing devices with enhanced characteristics.Open Access funding provided by the Qatar National Library. This work was supported by both Qatar National Research Fund (QNRF) under a Grant Number UREP21-035-2-013, and Qatar University fund under a Grant Number QUCG-CAS-20182019-1. The SEM/EDS measurements were accomplished in the Central Laboratories unit at Qatar University. Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations

Size-selected fabrication of alloy nanoclusters by plasma-gas condensation

This work reports on the production of alloy Ti-Cu nanoclusters by magnetron sputtering and plasma-gas condensation inside an ultra-high compatible system. Inert-gas was introduced inside a source chamber to generate plasma, sputter material from its target, and establish plasma-gas condensation. The nanocluster size and yield were controlled by adjusting the nanocluster source conditions: inert-gas flow rate fAr, aggregation length L, and sputtering discharge power P. Nanoclusters were produced by three-body collision that created nanocluster embryo, and grew further by two-body collision. The dependence of nanocluster size on nanocluster source conditions was modeled using a homogeneous nucleation model where a nanocluster grows from embryo by nanocluster-nanocluster collision and vapor condensation. Controlled oxidation of ionized nanocluster was conducted in-situ which was found to affect nanocluster charge but retain its size. The nanoclusters were deposited on SiO2/Si substrates with pre-formed metal electrodes to produce percolating nanocluster devices. Those devices have useful applications in many fields such as photoelectrochemical diodes for production of hydrogen fuel. 2018 Elsevier B.V.The author would like to acknowledge the financial support of Qatar University - grant number ( QUUG-CAS-DMSP-15?16-20 )

Graphene-based nanopore approaches for DNA sequencing: A literature review

DNA (deoxyribonucleic acid) is the blueprint of life as it encodes all genetic information. In genetic disorder such as gene fusion, copy number variation (CNV) and single nucleotide polymorphism, DNA sequencing is used as the gold standard for successful diagnosis. Researchers have been conducting rigorous studies to achieve genome sequence at low cost while maintaining high accuracy and high throughput, as such sequencer devices have been developed which led to the evolvement of this technology. These devices are categorized into first, second, and third DNA sequencing generations. One successful endeavor for DNA sequencing is nanopore sequencing. This specific method is considered desirable due to its ability to achieve DNA sequencing while maintaining the required standards such as low cost, high accuracy, long read length, and high throughput. On the other hand, non-nanopore sequencing techniques require extensive preparation as well as complex algorithms, and are restricted by high cost, small throughput, and small read lengths. In this review, the concepts, history, advances, challenges, applications, and potentials of nanopore sequencing are discussed including techniques and materials used for nanopore production and DNA translocation speed control. Additionally, in light of the importance of the nanopore material configuration and fabrication, graphene which is a common and effective material will be discussed in the context of nanopore fabrication techniques. Finally, this review will shed light on some nanopore-related investigations in the area of molecular biology. � 2018 Elsevier B.V.The authors would like to acknowledge the financial support by United Arab Emirates University with Fund number 31R128.Scopu

Defect states in amorphous Ge₂Sb₂Te₅ phase change material

Steady-state photoconductivity measurements in the temperature range 100–300 K on amorphous Ge2Sb2Te5 thin film prepared by dc sputtering are analyzed. The dark conductivity is thermally activated with a single activation energy that allocates the position of the Fermi level approximately in the middle of the energy gap relative to the valance band edge. The temperature dependence of the photoconductivity ensures the presence of a maximum normally observed in chalcogenides with low- and high-temperature slopes, which predict the location of discrete sets of localized states (recombination levels) in the gap. The presence of these defect states close to the valence and conduction band edges leaves the quasi Fermi level shifts in a continuous distribution of gap states at high temperatures, as evidenced from the γ values of the lux–ampere characteristics. </jats:p

Investigation of flexible polymer-Tl2O3 nanocomposites for x-ray detector applications

We report on the synthesis and characterization of composite semiconducting polymer – nanoparticle membranes for X-ray detection applications. The membranes are made of poly(vinyl alcohol) (PVA) organic polymer that is doped with ionic liquid (IL) to control its electrical conductivity. Tl2O3 nanoparticles with different weight concentrations are added to the polymer, and membranes are produced using solution casting method. The nanoparticles are synthesized using a microwave assisted technique under controlled temperature and pressure, and their average size is 13.0 ∓ 1.9 nm. Structural and compositional tests confirm the fabrication of homogeneous polymer-nanoparticle films. Electrical impedance tests are conducted as a function of nanoparticle concentration and temperature for the membranes, and they reveal that the dc electrical resistance of the membranes decreases with increasing both nanoparticle concentration and temperature. The activation energy was found to increase with increasing nanoparticle concentration. The membranes are utilized as conductometric X-ray sensors, and their response increases with increasing X-ray generator voltage. The fabricated composite membranes exhibit semiconducting properties, easy to fabricate, low cost, and qualify practical device utilization in the X-ray dosimetry sector.This work was supported by Qatar University under grants number QUCP-CAS-17\18-1 and QUCG-CAS-2018\2019-1 .Scopu

Investigation of Proton Diffusion Coefficient for PbO2 Prepared from Intermediate Oxides

Lead dioxide was extracted from used batteries, and used to synthesize the following intermediate oxides by heating at different temperatures: Pb12O19, Pb12O17, and Pb3O4. Each of the prepared intermediate oxide was subject to sulfuric acid with 1.28 g cm–3. X-ray diffraction (XRD) results showed that the sample prepared from Pb12O19 only had a pattern similar to that of the starting PbO2 with α-PbO2 and β-PbO2 phases. The measurements of H+ proton diffusion coefficient (DH+) of the different samples showed that the sample prepared from Pb12O19 had better electrochemical performances than the starting PbO2. This kinetics reflects the proton insertion mechanism in PbO2, i.e. the sample prepared from Pb12O19 has a large amount of structural water in OH– hydroxyl form. This amount contributes more in the PbO2 reduction mechanism. In addition, the DH+ value of the sample prepared from Pb12O19 is significantly higher than that of starting PbO2, which confirms this hypothesis. X-ray diffraction analysis, thermogravimetric and differential thermogravimetry analysis, and cyclic voltammetry reduction at different scanning rates were used to investigate the samples. This work contributes to environment preservation by recycling of used lead dioxide and reduction of the hazard of its disposal on water.Scopu

Fabrication and characterization of size-selected Cu nanoclusters using a magnetron sputtering source

Copper nanoclusters are used widely in applications such as glucose and gas sensors. A physical method is used to produce copper nanoclusters utilizing an ultra-high vacuum (UHV) system. Using a quadrupole mass filter (QMF), the size distribution of the nanoclusters is determined. It is found that varying the source parameters controls the size of the produced Cu nanoclusters. Increasing the aggregation length increases the nanocluster size. Varying the inert gas flow rate has a minor effect on the size at low aggregation length. On the other hand, at high aggregation length the size increases with increasing the gas flow. The results are interpreted in terms of the nucleation time and a two-body collision model between nanoclusters. Moreover, the band gap is measured for different sizes of CuO nanoclusters. ? 2018 Elsevier B.V.Center for Innovative Technology, United Arab Emirates UniversityScopu

Investigation of the Formation Mechanisms of Pd Nanoclusters Produced Using a Magnetron Sputtering Source

We report on the fabrication of palladium (Pd) nanoclusters using a dc magnetron sputtering source. The sputtering source produces ionized nanoclusters that enable the study of the nanoclusters' size distribution using a quadrupole mass filter. In this work, the dependence of Pd nanoclusters' size distribution on various source parameters, such as the inert gas flow rate, and aggregation length have been investigated in details. This work demonstrates the ability of tuning the palladium nanoclusters' size by proper optimization of the source operation conditions. © (2011) Trans Tech Publications, Switzerland

Doped conductive polymers and single-walled carbon nanotubes as charge storage devices

Single-walled carbon nanotubes (SWCNTs), introduced as nano-fillers, were used as charge storage elements. Organic semiconducting polymers were produced by doping organic plasticizers with nonconductive polymers. The nano-fillers were embedded along with organic semiconducting and insulating polymers in constructing metal-insulator-semiconductor (MIS) capacitors classified as organic capacitors. The capacitors were constructed by conventional spin-coating method with metallic electrodes fabricated by means of thermal evaporation. A comparative study was investigated on two device configurations that were built. One with the use of the organic semiconducting polymers and the other with commercially available doped silicon wafer as the semiconductor. Capacitance versus voltage measurements were analyzed on the two configurations to evaluate the storage performance of the devices. The results showed that the device that contained the organic polymeric charge transport layer stored more charge in the SWCNT nano-fillers when compared with the device that contained the silicon wafer. The results also depicted that the embedded SWCNTs were responsible for storing the charge when compared with reference devices that did not contain these nano-fillers